linux-kernel - Re: Testing wanted for Linux NFC subsystem

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Message-ID: <YJ1Hr/hov9I42GK1@gerhold.net>
Date:   Thu, 13 May 2021 17:37:19 +0200
From:   Stephan Gerhold <stephan@...hold.net>
To:     Mark Greer <mgreer@...malcreek.com>
Cc:     Frieder Schrempf <frieder.schrempf@...tron.de>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-nfc@...ts.01.org,
        Alex Blasche <alexander.blasche@...io>,
        phone-devel@...r.kernel.org
Subject: Re: Testing wanted for Linux NFC subsystem

On Thu, May 13, 2021 at 07:48:55AM -0700, Mark Greer wrote:
> On Thu, May 13, 2021 at 01:49:53PM +0200, Stephan Gerhold wrote:
> > I have a couple of "recycled" smartphones running mainline Linux
> > and some of them do have NFC chips. I have two with NXP PN547
> > (supported by nxp,nxp-nci-i2c), one with Samsung S3FWRN5
> > (samsung,s3fwrn5-i2c) and even one with Broadcom BCM2079x I think
> > (this one does not have a driver for the Linux NFC subsystem sadly).
> > 
> > +Cc phone-devel@...r.kernel.org, in case other people there are
> > interested in NFC :)
> > 
> > The NXP/Samsung ones seems to work just fine. However, since there are
> > barely any userspace tools making use of Linux NFC all my testing so far
> > was limited to polling for devices with "nfctool" and being happy enough
> > when it realizes that I hold some NFC tag close to the device. :S
> 
> There is a user-level daemon that is the counterpart for the in-kernel
> NFC subsystem.  It is called neard and is available here:
> 
> 	git://git.kernel.org/pub/scm/network/nfc/neard.git
> 
> There are a few test script in it that will let you read and write NFC
> tags, and do some other things.  We can add some more tests to that set
> as we go.
> 

Yeah, I packaged that for Alpine Linux / postmarketOS.
"nfctool" also comes from "neard" as far as I can tell :)

I think I also played with the Neard test scripts a bit at some point,
and managed to read some NFC tag thing inside an old Yubikey NEO
that I found, but didn't really know what else to do.

> > I would be happy to do some more testing if someone has something useful
> > that can be tested. However, I guess ideally we would have someone who
> > actually uses Linux NFC actively for some real application. :)
> 
> Ideally, you should have some NFC tags of various types.  Types 2, 3,
> 4A, 4B, and 5 tags are supported.  Peer-to-peer mode is supported too
> so you should be able to transfer data from one of your phones to the
> other over NFC (and do a BT hand-over, if you're interested).
> 

I guess this is where I kind of lack hardware as well at the moment,
I don't have any programmable NFC tags at the moment (although I guess
those should be quite cheap). I might play with the peer-to-peer mode
a bit when I find time.

> Note that the specified range for NFC is only 4 cm and poor antenna
> design, etc. means that the actual range is usually much less (e.g.,
> they amost have to touch).  Also note that there are timing constraints
> so you may need to make the scheduling priority of the interrupt thread
> of your NFC driver real-time.
> 

Yeah I noticed, always need to search for a while to find the right spot
on the phone. :)

Stephan